New iminophosphorane-mediated synthesis of thieno[3′,2′:4,5]thieno[3,2-d]pyrimidin-4(3H)-ones and 5H-2,3-dithia-5,7-diaza-cyclopenta[c,d]indenes |
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Authors: | Ming-Guo Liu Yang-Gen Hu |
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Institution: | a Key Laboratory of Pesticide & Chemical Biology of Ministry of Education, Central China Normal University, Wuhan 430079, PR China b Hubei Key Laboratory of Natural Products Research and Development, China Three Gorges University, Yichang 443002, PR China |
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Abstract: | Mono(iminophosphorane) 4 was selectively prepared from the reaction of 3,4-diaminothieno2,3-b]thiophene 3 with excess triphenylphosphine, C2Cl6, and Et3N due to intramolecular double hydrogen bond formation. Mono(iminophosphorane) 4 reacted with aromatic isocyanates to give stable carbodiimides 8, which were further treated with aliphatic secondary or primary amines to give 2-amino substituted thieno3′,2′:4,5]thieno3,2-d]pyrimidin-4(3H)-ones 10 or 12 in the presence of a catalytic amounts of EtO−Na+. However, in the presence of a catalytic amounts of potassium carbonate, the carbodiimides 8 were transformed into previously unreported 5H-2,3-dithia-5,7-diaza-cyclopentac,d]indenes 13 via direct cyclization in high yields. The reaction of carbodiimides 8 with phenols in the presence of a catalytic amounts of potassium carbonate gave a mixture of 2-aryloxy substituted thieno3′,2′:4,5]thieno3,2-d]pyrimidin-4(3H)-ones 14 and 13. X-ray structure analysis of 10m supported the structure and the proposed reactivity of amino group. |
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